In an IPv6 network of nodes, neighbor discovery (ND) configures IPv6 addresses of the nodes (hosts and routers), discovers other nodes on link, and discovers routers to forward data packets. The conventional IPv6 ND protocol is specified in the IETF (Internet Engineering Task Force) standard RFC 4861, which defines Router Solicitation (RS), Router Advertisement (RA), Neighbor Solicitation (NS), Neighbor Advertisement (NA), and Redirect messages for neighbor discovery purposes. All the standards referenced herein are well known and readily available from a number of sources.
In the conventional IPv6 network, the routers broadcast the RA messages periodically, the hosts receive the RA messages from the routers, configure their IPv6 addresses and select routers for packet forwarding. According to RFC 4861, a host can receive the RA message from at least one router, that is, 1-hop communication between the router and the host. RFC 4861 does not consider sleeping hosts. A sleeping host is a node not actively transmitting. Therefore, RFC 4861 is not suitable for emerging low power and lossy networks (LLNs), where sleeping host must be supported.
To meet requirements of the LLNs, IETF 6LoWPAN (IPv6 over Low-Power Wireless Personal Area Networks) Working Group (WG) has developed a new ND protocol RFC 6775, which optimizes the IPv6 ND protocol RFC 4861 for LLNs. The optimizations include host-initiated interactions to support sleeping hosts, and multi-hop distribution of a prefix by introducing 6LoWPAN Router. Host-initiated interaction removes the need for periodic or unsolicited RA message from the routers to the hosts. 6LoWPAN routers can transmit and receive the RA and RS messages and forward and route IPv6 packets, and are present only in the route-over a topology, where routing decisions take place at the network layer and hosts are connected to the 6LoWPAN border router through the use of intermediate network layer (IP layer) routing.
A route-over topology typically includes a 6LoWPAN border router, a set of 6LoWPAN routers, and hosts. Hosts are typically multiple hops away from a 6LoWPAN border router. The 6LoWPAN routers do not configure the IPv6 prefix, which is configured at 6LoWPAN border router. Hosts in the 6LoWPAN network receive the RA message from the 6LoWPAN router in a multi-hop manner or directly from the 6LoWPAN border router. In other words, communication between the host and the router is also I-hop.
Security has been added to IPv6 neighbor discovery. U.S. Patent Publication 20120084568 describes a secure neighbor discovery protocol for resource limited devices in low-power and lossy networks. That protocol uses reduced size public key and signature, and simpler signature calculations in comparison to a secure neighbor discovery protocol for securing neighbor discovery protocol communications that are more suitable for low-power and lossy networks.
IPv6 neighbor discovery has been extended to specific networks. For example, U.S. Patent Publication 20130091269 describes a distributed IPv6 neighbor discovery for large data switching systems, in which all neighbor discovery operations and functionality are distributed to a switch device. Each neighbor discovery process in the switch device operates as an individual neighbor discovery router node.
U.S. Pat. No. 8,335,505 describes neighbor discovery in an IPv6-based mobile system. A mobile station includes a mapping table storing a connection identifier (CID) prefix and a neighbor identifier, a controller generating a CID with respect to a message that is transmitted by referring to the mapping table, and a message transmitter for transmitting the message to a base station connected the mobile station, by using the CID.
A smart meter or sensor node is different from a host in the conventional IPv6 network and the 6LoWPAN network because the typical node, when compared to the host, has limited resources, such as processing and transmitting power, memory, etc. However, nodes such as smart meters are typically mains-powered and do not sleep. Therefore, the smart meter is different from a host in the 6LoWPAN network.
The main difference is that in the IPv6 network and the 6LoWPAN network, the host can reach at least one router. This may not be the case in the smart meter network. In the smart meter network, the concentrators only operate as routers. Most of the smart meters are multiple hops away from the concentrators. There are no 6LoWPAN routers to distribute the prefix from the concentrators to the smart meters because installation of 6LoWPAN router in smart meter network is impractical for cost reason. Neighbor discovery methods for large switching systems and for mobile systems are not suitable for the smart meter networks. Accordingly, it is desired to provide a neighbor discovery method for smart meter networks.